Arc evaporation techniques for physical vapor deposition have been long known in the vacuum coating industry. This coating technique employs an electric arc, wherein an arc is intentionally struck on a material to be vaporized, i.e. target, and the resultant electrical energy contained in the arc then vaporizes the material, thus creating a vapor stream. The elements present in such apparatus can be generalized to include an electrically biased coating “target” material, which serves as one electrode (usually the cathode). Another portion of the deposition chamber is biased at a second potential, different from the target potential, and acts as the second electrode (usually the “anode”) of the electric arc discharge circuit. An arc-initiating trigger element is positioned in proximity to the cathode source and is positively biased with respect to the cathode. The arc trigger element is momentarily allowed to engage the surface of the cathode material, establishing a current flow path through the trigger and cathode. As the trigger element is removed from engagement with the cathode source, an electrical arc is initiated, which is thereafter maintained between the cathode and the anode electrodes. The arc then provides the energy for vaporizing the target material constituting the cathode. The electrical discharge is carried out in a chamber that is normally maintained at negative pressure. The vaporized source material includes atoms of the source material, ions of such atoms, molecules containing atoms of the source material, ions of such molecules, electrons and radicals. The ionized portion of the vapor cloud, associated electrons and radicals are called “plasma”. The high-energy point on the cathode at which the vaporization is occurring is often called the “cathode spot.”
Several techniques are known for coating by physical vapor deposition using the vacuum arc discharge. The various techniques can be differentiated by their attempts to improve design performances and coating process parameters. Historically, the first attempts employed only the natural physical properties of the arc discharge plasma produced by cathode spots for a coating deposition. Latter design efforts focused on stabilization of the discharge on the cathode surface, improving cathode material utilization, and improving the reliability of the arc ignition. Stabilization was usually achieved using some magnetic, electrostatic, or physical method for controlling or limiting movement of the cathode spot. The resulting vapor, neutral and ionized, and plasma stream generated by the cathode spots diffused during propagation. The vapor density naturally decreased with the square of the distance between the cathode and the substrate. The magnetic fields that were meant to control cathode spot movement were not strong enough to substantially change the vapor flow parameters.
U.S. Pat. No. 2,972,695 (1961) to Wroe relates to cathodic arc stabilization, which has basically remained unchanged in the plating industry.
U.S. Pat. No. 3,783,231 (1974) to Sablev et al. describes a method of vacuum-evaporization of metals under the action of an electric arc and use of a magnetic field.
U.S. Pat. No. 4,448,799 (1984) to Bergman et al. describes a trigger apparatus and method for striking an electrical arc at the surface of a coating source material within a vapor deposition chamber is disclosed. This invention relates generally to electric arc vacuum physical vapor deposition coating systems, and in particular to a trigger apparatus and metal for striking an electric arc on the coating source electrode material to initiate generation of a coating plasma within the deposition chamber.
U.S. Pat. No. 4,511,593 (1985) to Brandolf describes a method and apparatus for vapor depositing node-free coatings on substrate surfaces, preserving the pre-coating surface finish dimensions of the substrate.
U.S. Pat. No. 4,556,471 (1985) to Bergman et al. describes a gap used in preventing arc from going over the cathode edge and relates to an electrode mounting assembly for an electric arc vapor deposition machine.
U.S. Pat. No. 4,645,895 (1987) to Boxman et al. describes a method of surface-treating a workpiece characterized in applying one or more short-duration electrical pulses to produce, for each pulse, a high amplitude short-duration electrical discharge between the workpiece, serving as the anode, —and coating target material serving as the cathode.
U.S. Pat. No. 4,762,756 (1988) to Bergmann et al. describes a method for the thermochemical surface treatment of workpieces in reactive gas plasma.
U.S. Pat. No. 4,919,968 (1990) to Buhl et al. describes a continuous vapor deposition on the cathode surface with a metal compound which can be broken down, by which accelerated migration of the vapor emitting hot spots is forced in such a way that the hot spots migrate away from a particular site before spatter formation starts.
U.S. Pat. No. 4,929,321 (1990) to Buhl describes a method and arrangement for vacuum coating of workpieces by arc evaporation, comprising of at least one evaporating cathode with a surface to be evaporated and an axis of the cathode intersecting the cathode surface.
U.S. Pat. No. 5,037,522 (1991) to Vergason describes an electric arc vapor deposition device in which the negative side of an arc power supply is switched back and forth between the two ends of a cylindrical cathode using an arc sensor and related electronics to cause the arc to travel back and forth along the length of the cathode.
U.S. Pat. No. 5,126,030 (1992) to Tamagaki et al. describes a cathodic arc deposition method and apparatus, including an arc evaporation source containing a film forming material.
U.S. Pat. No. 5,269,896 (1993) to Munemasa et al. describes cathodic arc deposition system and includes a cathode made of a film forming material, a shield surrounding a circumferential side of the cathode with a gap, a vacuum chamber having the cathode and the shield therein, and a substrate to have deposited at a surface.
U.S. Pat. No. 5,269,898 (1993) to Welty et al. describes a method for depositing a coating onto a substrate using vacuum arc evaporation from a substantially cylindrical cathode surrounded by an electromagnetic coil for arc control. This method also utilizes an arc sensor and electronics for switching current between two ends of the cathode.
U.S. Pat. No. 5,298,137 (1994) to Marshall describes an emission enhanced sputtering magnetron apparatus which includes an elongated rod or bar like cathode jacketed by a target material.
U.S. Pat. No. 5,744,017 (1998) to Tamagaki et al. describes a vacuum arc deposition apparatus which includes arc power sources having cathodes connected to both ends of an evaporation source; exciting coils disposed at positions axially outwardly far from both the ends of the evaporation source so as to be coaxial with the evaporation source; and coil power sources independently connected to the exciting coils.
U.S. Pat. No. 5,895,559 (1999) to Christy describes a cathodic arc cathode provided with a gap and an insulating ring in close proximity to the underside of a cantilevered edge of the target. The patent also describes two high resistivity elements to manage the arc movement about the cathode.
U.S. Pat. No. 5,932,078 (1999) to Beers et al. describes an apparatus for applying material by cathodic arc deposition to a substrate including a vessel means for maintaining a vacuum in the vessel, a cathode, a contactor, means for selectively sustaining an arc of electrical energy between the cathode and the anode, and an actuator.
U.S. Pat. No. 5,972,185 (1999) to Hendricks et al. describes an apparatus for applying material by cathodic arc vapor deposition to a substrate including a vessel, apparatus for maintaining a vacuum in the vessel, an annular cathode having a bore and an evaporative surface extending between first and second end surfaces, apparatus for selectively sustaining an arc between the cathode and anode, and apparatus for steering the arc around the evaporative surface using an electromagnetic coil.
What is needed is an apparatus with more uniform and economical utilization of the target material for deposition; a relatively simple, economical and robust method of striking an arc; a self-sustaining electric arc triggering unit; a relatively simple, economical, and robust method of controlling and steering the arc movement as well as arc-speed on the desired target surface; ability to use higher currents to increase deposition rate; more efficient utilization of target material vapors for deposition to reduce waste deposits on the chamber walls thus further enhancing the deposition rate; more efficient method of packaging a cathode/anode electrode combination; improvement in coating uniformity on_larger surface areas; and lower equipment cost, maintenance cost and down-time. The present invention addresses these areas and resolves many deficiencies of prior art by stated improvements in several areas.